They are roving wiretaps to track multiple communications devices an individual may use; access business records; and what’s known as the “lone wolf” provision to watch an individual who may be hatching terror plots but isn’t part of a bigger group. Those three expire Dec. 31.

However, some Senate Judiciary Committee members, including chairman Patrick Leahy, want to add more privacy provisions. Any changes also have to go through the Senate Intelligence Committee which could raise more hurdles.

Mueller offered a staunch defense for the techniques, noting that the roving wiretaps were essential since individuals can have several cell phones at once and switch quickly. He also said that while the “lone wolf” tracking had not yet been used, it was important to have that capability available.

Senators Richard Durbin and Russ Feingold said in their own statement on Tuesday that they hoped to add stronger privacy protections in any extension of the three provisions. They also want to address so-called National Security Letters which are essentially subpoenas for personal records and have been used in larger numbers but have been harshly criticized for being overused.